Q: If the $$K_{sp} of Mg(OH)_2 is$$ $$1.8 \times 10$$^{-11}$$, what is the minimum $$[OH^-]$$ required to begin precipitating Mg(OH)_2 from a solution containing $$[$$Mg^{2+}$$] = 0.053$$ M?

$$[OH^-] = 5.8 \times 10$$^{-6}$$ M

Q: Which of the following is the correct relationship between pH and pOH in aqueous solution at 25°C?

$$\text{pH} + \text{pOH} = 14$$

Question 1

Which of the following best describes an amphiprotic substance?

Accepted Answer

A substance that can act as both an acid and a base by donating or accepting protons.

Question 2

Which of the following is NOT a strong acid?

Accepted Answer

HF

Question 3

According to the Lewis definition, which of the following is a Lewis acid?

Accepted Answer

$$Al^{3+}$$

Question 4

What is the value of $$K_w$$ for water at 25°C?

Accepted Answer

$$1.0 	imes 10$$^{-14}$$

Question 5

A solution has $$[H^+] = 2.0 	imes 10$$^{-3}$$ M. What is its pH?

Accepted Answer

pH = 2.70

Question 6

Which of the following combinations will create a buffer solution?

Accepted Answer

$$HCHO_2$$ and $$NaCHO_2$$

Question 7

What is the correct expression for the acid dissociation constant ($$K_a) $$for a weak acid $$HA$$?

Accepted Answer

$$K_a = \frac{[H^+][A^-]}{[HA]}$$

Question 8

A 0.100 M solution of HA has a pH of 4.25. What is the $$K_a of $$this acid?

Accepted Answer

$$K_a = 5.6 	imes 10$$^{-5}$$

Question 9

Which of the following statements about strong acids is TRUE?

Accepted Answer

The conjugate base of a strong acid is relatively stable.

Question 10

What is the pOH of a solution with $$[OH^-] = 1.0 	imes 10$$^{-5}$$ M?

Accepted Answer

pOH = 5

Question 11

If the $$K_{sp} of Mg(OH)_2 is$$ $$1.8 	imes 10$$^{-11}$$, what is the minimum $$[OH^-]$$ required to begin precipitating Mg(OH)_2 from a solution containing $$[$$Mg^{2+}$$] = 0.053$$ M?

Accepted Answer

$$[OH^-] = 5.8 	imes 10$$^{-6}$$ M

Question 12

Which of the following best explains why dissolving NaCl in water does NOT affect the pH of the solution?

Accepted Answer

NaCl is a salt of a strong acid and a strong base, so neither ion hydrolyzes in water.

Question 13

A buffer solution is most effective when:

Accepted Answer

It contains equal concentrations of a weak acid and its conjugate base.

Question 14

Which of the following is the correct relationship between pH and pOH in aqueous solution at 25°C?

Accepted Answer

$$	ext{pH} + 	ext{pOH} = 14$$

Question 15

Which of the following is a correct statement about the effect of adding a strong acid to a buffer solution?

Accepted Answer

The pH will decrease slightly, but not drastically.

Question 16

Calculate the percent ionization of a 0.10 M solution of a weak acid HA with $$[H^+]_{eq} = 1.3 	imes 10$$^{-3}$$ M.

Accepted Answer

1.3%

Question 17

Which of the following best describes the difference between the Arrhenius and Brønsted-Lowry definitions of acids and bases?

Accepted Answer

Arrhenius acids produce $$H^+ in $$water, while Brønsted-Lowry acids donate protons to any base.

Question 18

A solution is prepared by mixing 0.10 M HCl and 0.10 M $$HCHO_2 ($$formic acid, $$K_a = 1.8 	imes 10$$^{-4}$$). Which acid will primarily determine the pH of the solution?

Accepted Answer

HCl, because it is a strong acid and will fully dissociate.

Question 19

Which of the following metal ions is most likely to act as a weak acid in aqueous solution?

Accepted Answer

$$Al^{3+}$$

Equilibria, Precipitation, and Acid-Base Chemistry: Study Notes

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